The evolution of sensory and neurosecretory cell types in bilaterian brains [Elektronische Ressource] / vorgelegt von Kristin Teßmar-Raible

Informations

• Publié par: philipps-universitat_marburg
• Publié le: 01 janvier 2004
• Nombre de lectures: 16
• Langue: English
• Poids de l'ouvrage: 1 Mo

Extrait

The evolution of sensory and
neurosecretory cell types in bilaterian
brains
DISSERTATION
zur Erlangung des Doktorgrades der Naturwissenschaften
Doctor rerum naturalium
(Dr. rer. nat.)
dem Fachbereich Biologie
der Philipps-Universität Marburg
vorgelegt von
Dipl.-Biol. K. G. Kristin Teßmar–Raible
aus Görlitz
Marburg/ Lahn 2004Vom Fachbereich Biologie
der Philipps-Universität Marburg als Dissertation am
angenommen.
Erstgutachterin: Prof. Dr. Monika Hassel
Zweitgutachterin : Prof. Dr. Renate Renkawitz-Pohl
Tag der mündlichen Prüfung:The evolution of sensory and
neurosecretory cell types in bilaterian
brainsTo my parents and my husband for their encouragement and patienceAcknowledgements
I am very thankful to the following persons in Marburg and Heidelberg that made
this study possible: Dr. Monika Hassel at Marburg University for the supervision of
my PhD thesis and correction of the text; Dr. Detlev Arendt at the EMBL in
Heidelberg for giving me the opportunity to spend time in his lab as a guest and for
scientific advice; Dr. Monika Hassel, Dr. Renate Renkawitz-Pohl and the other
members of my defense committee for reviewing this thesis.
I want to acknowledge all members and guests of the Arendt lab, in particular
Sebastian Klaus, Heidi Snyman, and Patrick Steinmetz, for for their help, their useful
critical comments, and the interesting scientific discussions; in addition, I want to
thank Heidi Snyman for very reliable practical help, especially with degenerated
PCRs, minipreps, and restriction digests; and Dr. Detlev Arendt for minipreps of the
Pdu-barH1 cloning. Moreover, I thank Dr. Florian Raible and Dr. Detlev Arendt for
extensive critical feedback on previous versions of this text.
There were certainly some difficult times when I was glad to be able to rely on the
support and advise of more experienced people. For this, I am especially grateful to
Dr. Florian Raible, Dr. Detlev Arendt, Dr. Oliver Hobert, Dr. Jochen Wittbrodt and
Dr. Gary Ruvkun.
I am thankful to Monika Beutelspacher and Dr. Herrmann Froehlich and the entire
Boehringer Ingelheim Foundation not only for the financial support, that enabled me
to perform this PhD study, but also for their encouragement and reliability.
Much of my plannings and theoretical work depended on literature not easily avaible
via the internet. I therefore thank the EMBL Szilárd librarians, especially David
Wesley, who got many articles and books for me.
I express my thanks for materials to Dr. Nicole Rebscher (anti-rabbit anti-
RFamide(s) antibody), Alena Shkumatava and Dr. Carl Neumann (initial aliquots of
cyclopamine).
My special gratitude belongs to my husband Dr. Florian Raible, who is my truly best
partner for both my scientific and personal life. Finally, I feel indebted to my parents
and parents in law for their generous advice and help.Table of contents
Acknowledgements ..........................................................................................................................i
Table of contents ............................................................................................................................ii
Index of Figures............vii
Index of tables .............................................................................................................................viii
1 INTRODUCTION ..........................................................................................................1
1.1 Defining homology relationships across Bilateria..........................................................2
1.2 Platynereis dumerilii – an ancestral organism for the comparative study of animal
development and genome evolution.................................................................................4
1.3 The concept of homologous cell types .............................................................................8
1.4 The bilaterian nervous system........................................................................................12
1.4.1 The apical organ and its cell types............................................................................................... 14
1.4.2 Neurosecretory cells..................................................................................................................... 16
1.4.3 The vertebrate hypothalamus....................................................................................................... 19
1.4.4 Cell types of photosensory structures.......................................................................................... 21
1.5 Aim of this thesis.............................................................................................................23
2 RESULTS ......................................................................................................................25
2.1 Indications for a conserved molecular organisation of Bilaterian brains ...................26
2.1.1 Pdu-nk2.1 is expressed in the median brain anlage complentary to Pdu-pax6..........................27
2.2 Molecular characterisation of the ciliary and rhabdomeric photoreceptor cell types
in Platynereis dumerilii..................................................................................................31
2.2.1 Ciliary photoreceptor cell types................................................................................................... 31
2.2.2 The opsin active in Platynereis ciliary PRCs closer relates to vertebrate rod and cone opsins
than to canonical invertebrate opsins.................................................................................32
2.2.3 The Platynereis ciliary photoreceptor cells express rx, a transcription factor specific for the
differentiating vertebrate rods and cones...........................................................................34
2.2.4 Rhabdomeric photoreceptor cell types ........................................................................................ 37
2.2.5 Platynereis atonal homolog/Pdu-ath is transiently expressed in the larval eye precursors .......38
2.2.6 Pdu-brn3 demarcates the larval eye region.40
2.2.7 Cloning of Pdu-barH1 as additional rhabdomeric PRC marker gene ........................................42
2.2.8 Larval, but not adult eye regions are histaminergic ....................................................................44
2.3 Molecular characterisation of neuroendocrine regions and cell types in Platynereis
.........................................................................................................................................44iiiTABLE OF CONTENTS
2.3.1 The Platynereis median episphere expresses homologs of transcription factors that are highly
specific for the median/ventral forebrain in vertebrates ...................................................45
2.3.2 Orthologs of sim, pou3 and gsx transcription factors, essential for the formation of
hypothalamic neuropeptidergic neurons, are also present in the apical organ region of
Platynereis larvae................................................................................................................ 54
2.3.3 Analysis of markers that indicate specific differentiated cell types and exist in the
median/ventral forebrain of vertebrates.............................................................................60
2.3.4 The lipophilic dye DiI stains a distinct set of cells in Platynereis larvae, including cells of the
apical organ......................................................................................................................... 76
2.4 A whole mount in situ hybridization screen uncovers additional genes involved in
bilaterian brain development .........................................................................................78
2.5 The Hedgehog (Hh) pathway is involved in the development of the episphere in the
Platynereis dumerilii trochophora.................................................................................81
2.5.1 Cloning and expression of members of the Hh-pathway in Platynereis dumerilii ....................83
2.5.2 Interfering with the hh-pathway using the drug cyclopamine ....................................................86
3 DISCUSSION................................................................................................................98
3.1 Equivalence between bilaterian photosensory and neurosecretory systems on
different levels.................................................................................................................99
3.2 Common ancestry/homology is the most likely cause for the occurence of equivalent
cell types across Bilateria ............................................................................................102
3.2.1 The master control gene concept: a valid alternative explanation?..........................................103
3.2.2 The molecular fingerprint is a useful criterium for cross-species comparisons.......................105
3.3 Is there conservation on the level of brain areas across Bilateria?...........................105
3.3.1 Robustness in molecular specification of regions within phyla as prerequisite for
interphyletic comparison..................................................................................................107
3.3.2 No conservation of otx, bf-1, emx regions? ............................................................................